Multi-infarct dementia (MID) is the most common form of vascular dementia, which is a deterioration in mental function caused by strokes. "Multi-infarct" means that multiple areas in the brain have been injured due to a lack of blood.

MID affects approximately 4 out of 10,000 people. It is estimated that 10 - 20% of all dementias are caused by strokes, making MID the third most common cause of dementia in the elderly, behind Alzheimer's disease and DLBD (dementia of Lewy bodies). MID affects men more often than women. The disorder usually affects people over 55, with the average onset at age 65.

The symptoms of MID vary. Memory loss is often an early symptom of the disorder, followed by trouble making judgments. This often progresses to delirium, hallucinations, and thinking problems. Personality and mood changes can also occur. Lack of emotion and motivation, withdrawal, and extreme excitability (agitation) are common. Confusion that occurs or is worse at night is another common symptom.

Risk factors for MID include a history of stroke, hypertension, smoking, and atherosclerosis.

Some research suggests that MID may cause Alzheimer's disease or make it get worse faster. MID may be misdiagnosed as Alzheimer's, or may be found in addition to Alzheimer's disease.

• Awareness of mental deterioration, which may cause frustration, depression, anxiety, stress, and tension
• Dementia (slowly progressive memory loss) with lack of awareness of mental deterioration and:
  • Difficulties with attention, concentration, judgment, and behavior
  • Confusion, disorientation
  • Hallucinations (hearing sounds or seeing things which are not there) and delusions
  • Uncoordinated or weak movements
  • Aphasia (impaired language ability)
  • Personality changes
  • Progressive decreases in multiple brain functions
• Withdrawal from social interaction
  • Inability to interact in social or personal situations
  • Inability to maintain employment
• Decreased ability to function independently
• Decreased interest in daily living activities
• Lack of spontaneity
• Localized numbness or tingling
• Swallowing difficulty
• Sudden involuntary laughing or crying (emotional instability)
• Urinary incontinence

The disorder is diagnosed based on history, symptoms, signs, and tests, and by ruling out other causes of dementia, including dementia due to metabolic causes. History may include a past stroke or hypertension. History of the dementia often shows stepwise progression of the condition -- periods of abrupt decline alternating with stable periods of minimal decline. Other characteristics that suggest multi-infarct dementia rather than Alzheimer's disease include: abrupt onset, physical complaints, emotional changes, and localized neurologic signs (modified Hachinski ischemia scale).

A neurologic examination shows variable deficits depending on the extent and location of damage. There may be multiple, localized areas with specific loss of function. Weakness or loss of function may occur on one side or only in one area. Abnormal reflexes may be present. There may be signs of cerebellar dysfunction such as loss of coordination.

A head CT scan, and even more likely, MRI of the brain may show changes that suggest multi-infarct dementia because areas of dead tissue may be visible.